Gamma-ray Burst 251214B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:11:32 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1423875,   Seg_Num: 0
GRB_RA:          330.217d {+22h 00m 52s} (J2000),
                 330.561d {+22h 02m 15s} (current),
                 329.554d {+21h 58m 13s} (1950)
GRB_DEC:          -9.167d {-09d 10' 00"} (J2000),
                  -9.041d {-09d 02' 28"} (current),
                  -9.408d {-09d 24' 27"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       942 [cnts]    Image_Peak=97 [image_cnts]
TRIGGER_DUR:     0.256 [sec] 
TRIGGER_INDEX:   123     E_range: 25-100 keV
BKG_INTEN:       14402 [cnts]
BKG_TIME:        32523.14 SOD {09:02:03.14} UT
BKG_DUR:         8 [sec]
GRB_DATE:        21023 TJD;   348 DOY;   25/12/14
GRB_TIME:        32537.54 SOD {09:02:17.54} UT
GRB_PHI:          80.63 [deg]
GRB_THETA:         7.05 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     22.02 [sigma]
IMAGE_SIGNIF:    8.62 [sigma]
MERIT_PARAMS:     +1  +0  +0  -2  +2  -1  +0  +0 -39  +0 
SUN_POSTN:       261.97d {+17h 27m 53s}  -23.23d {-23d 13' 47"}
SUN_DIST:         66.84 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      197.98d {+13h 11m 55s}  -10.93d {-10d 56' 02"}
MOON_DIST:       128.78 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       48.74,-45.97 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      329.08,  2.80 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This Notice was delayed by more than 60 sec past the end of the trigger integration interval;  
COMMENTS:        probably due to it occurring during a Malindi downlink session.  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 92.59,7.49 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(1.0<100sec) coincident with the FERMI_GBM event (trignum=787395743).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:12:01 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     1423875,   Seg_Num: 0
POINT_RA:        330.212d {+22h 00m 51s} (J2000)
POINT_DEC:        -9.170d {-09d 10' 11"} (J2000)
IMG_START_DATE:  21023 TJD;   348 DOY;   25/12/14
IMG_START_TIME:  32598.22 SOD {09:03:18.22} UT,   60.7 [sec] since BAT Trigger Time
COUNTS:          20    Min_needed= 20
STD_DEV:         34.92   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        1    Max_iter_allowed= 4
ERROR_CODE:      3
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        Standard deviation too large.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:02:47 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      45
TRIGGER_NUM:     787395743
GRB_RA:          326.567d {+21h 46m 16s} (J2000),
                 326.932d {+21h 47m 44s} (current),
                 325.861d {+21h 43m 27s} (1950)
GRB_DEC:         -22.800d {-22d 48' 00"} (J2000),
                 -22.679d {-22d 40' 44"} (current),
                 -23.031d {-23d 01' 52"} (1950)
GRB_ERROR:       21.50 [deg radius, statistical plus systematic]
GRB_INTEN:       125 [cnts/sec]
DATA_SIGNIF:     5.80 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        21023 TJD;   348 DOY;   25/12/14
GRB_TIME:        32538.03 SOD {09:02:18.03} UT
GRB_PHI:         305.00 [deg]
GRB_THETA:        90.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      0.88
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      96%  GRB
2nd_MOST_LIKELY:   1%  Generic Transient
DETECTORS:       0,0,0, 1,1,0, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       261.97d {+17h 27m 52s}  -23.23d {-23d 13' 46"}
SUN_DIST:         59.28 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:      197.91d {+13h 11m 39s}  -10.90d {-10d 54' 07"}
MOON_DIST:       119.83 [deg]
MOON_ILLUM:      27 [%]
GAL_COORDS:       28.26,-48.04 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      321.13, -8.83 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214377/quicklook/glg_lc_medres34_bn251214377.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 192.92,2.58 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:03:04 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     787395743
GRB_RA:          319.650d {+21h 18m 36s} (J2000),
                 320.023d {+21h 20m 05s} (current),
                 318.931d {+21h 15m 43s} (1950)
GRB_DEC:         -23.280d {-23d 16' 47"} (J2000),
                 -23.170d {-23d 10' 10"} (current),
                 -23.491d {-23d 29' 27"} (1950)
GRB_ERROR:       9.53 [deg radius, statistical only]
DATA_SIGNIF:     7.80 [sigma]
DATA_INTERVAL:   1.024 [sec]
GRB_DATE:        21023 TJD;   348 DOY;   25/12/14
GRB_TIME:        32538.03 SOD {09:02:18.03} UT
GRB_PHI:         310.00 [deg]
GRB_THETA:        94.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       261.97d {+17h 27m 52s}  -23.23d {-23d 13' 46"}
SUN_DIST:         52.97 [deg]   Sun_angle= -3.9 [hr] (East of Sun)
MOON_POSTN:      197.92d {+13h 11m 40s}  -10.90d {-10d 54' 10"}
MOON_DIST:       113.91 [deg]
MOON_ILLUM:      27 [%]
GAL_COORDS:       25.12,-42.05 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      314.88, -7.24 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214377/quicklook/glg_lc_medres34_bn251214377.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_787395743.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:11:45 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     787395743
GRB_RA:          329.600d {+21h 58m 24s} (J2000),
                 329.957d {+21h 59m 50s} (current),
                 328.911d {+21h 55m 39s} (1950)
GRB_DEC:         -18.550d {-18d 33' 00"} (J2000),
                 -18.425d {-18d 25' 30"} (current),
                 -18.789d {-18d 47' 20"} (1950)
GRB_ERROR:       9.30 [deg radius, statistical only]
GRB_DATE:        21023 TJD;   348 DOY;   25/12/14
GRB_TIME:        32538.03 SOD {09:02:18.03} UT
GRB_PHI:         300.00 [deg]
GRB_THETA:        91.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       261.97d {+17h 27m 53s}  -23.23d {-23d 13' 47"}
SUN_DIST:         63.16 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      197.98d {+13h 11m 56s}  -10.94d {-10d 56' 05"}
MOON_DIST:       124.27 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       35.72,-49.42 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      325.28, -5.80 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214377/quicklook/glg_lc_medres34_bn251214377.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214377/quicklook/glg_locplot_all_bn251214377.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice was generated completely by automated pipeline processing.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the SWIFT_BAT event (trignum=1423875).

GCN Circular #43088
The Fermi GBM team reports the detection of a likely LONG GRB
At 09:02:18 UT on 14 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251214B (trigger 787395743.028482 / 251214377).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 329.6, Dec = -18.5 (J2000 degrees, equivalent to J2000 21h 58m, -18d 30'), with a statistical uncertainty of 9.3 degrees.
The angle from the Fermi LAT boresight is 91.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214377/quicklook/glg_skymap_all_bn251214377.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214377/quicklook/glg_healpix_all_bn251214377.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214377/quicklook/glg_lc_medres34_bn251214377.gif

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:13:42 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1423875,   Seg_Num: 0
GRB_RA:          330.217d {+22h 00m 52s} (J2000),
                 330.561d {+22h 02m 15s} (current),
                 329.554d {+21h 58m 13s} (1950)
GRB_DEC:          -9.167d {-09d 10' 00"} (J2000),
                  -9.041d {-09d 02' 28"} (current),
                  -9.408d {-09d 24' 27"} (1950)
GRB_DATE:        21023 TJD;   348 DOY;   25/12/14
GRB_TIME:        32537.54 SOD {09:02:17.54} UT
TRIGGER_INDEX:   123
GRB_PHI:          80.63 [deg]
GRB_THETA:         7.05 [deg]
DELTA_TIME:      0.00 [sec]
TRIGGER_DUR:     0.256 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     22.02 [sigma]
IMAGE_SIGNIF:    8.62 [sigma]
LC_URL:          sw01423875000msb.lc
SUN_POSTN:       261.97d {+17h 27m 54s}  -23.23d {-23d 13' 47"}
SUN_DIST:         66.84 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      198.00d {+13h 11m 59s}  -10.94d {-10d 56' 31"}
MOON_DIST:       128.76 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       48.74,-45.97 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      329.08,  2.80 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:           
COMMENTS:        The next comments were copied from the BAT_POS Notice:  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 92.59,7.49 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:14:32 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1423875,   Seg_Num: 0
POINT_RA:        330.212d {+22h 00m 51s} (J2000)
POINT_DEC:        -9.170d {-09d 10' 10"} (J2000)
POINT_ROLL:      248.557d
IMG_START_DATE:  21023 TJD;   348 DOY;   25/12/14
IMG_START_TIME:  32601.51 SOD {09:03:21.51} UT,   64.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.085
N_STARS:         55
X_OFFSET:        440 [pixels]
Y_OFFSET:        586 [pixels]
X_MAX:           1399 [pixels]
Y_MAX:           1545 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw01423875000msufc0063.fits
SUN_POSTN:       261.98d {+17h 27m 54s}  -23.23d {-23d 13' 47"}
SUN_DIST:         66.83 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      198.00d {+13h 12m 01s}  -10.95d {-10d 56' 42"}
MOON_DIST:       128.75 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       48.73,-45.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.07,  2.80 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:15:17 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1423875,   Seg_Num: 0
POINT_RA:        330.212d {+22h 00m 51s} (J2000)
POINT_DEC:        -9.170d {-09d 10' 10"} (J2000)
ROLL:            248.557d
IMG_START_DATE:  21023 TJD;   348 DOY;   25/12/14
IMG_START_TIME:  32601.51 SOD {09:03:21.51} UT,   64.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     787395838
X_OFFSET:        759 [pixels]
Y_OFFSET:        905 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       919
Y_GRB_POS:       1065
BINNING_INDEX:   1
IM_URL:          sw01423875000msuni0100.fits
SUN_POSTN:       261.98d {+17h 27m 54s}  -23.23d {-23d 13' 47"}
SUN_DIST:         66.83 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      198.01d {+13h 12m 02s}  -10.95d {-10d 56' 52"}
MOON_DIST:       128.74 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       48.73,-45.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.07,  2.80 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:15:27 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1423875,   Seg_Num: 0
POINT_RA:        330.212d {+22h 00m 51s} (J2000)
POINT_DEC:        -9.170d {-09d 10' 10"} (J2000)
ROLL:            248.557d
IMG_START_DATE:  21023 TJD;   348 DOY;   25/12/14
IMG_START_TIME:  32601.51 SOD {09:03:21.51} UT,   64.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     787395838
X_OFFSET:        759 [pixels]
Y_OFFSET:        905 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       919
Y_GRB_POS:       1065
BINNING_INDEX:   1
IM_URL:          sw01423875000msuni0100.fits
SUN_POSTN:       261.98d {+17h 27m 54s}  -23.23d {-23d 13' 47"}
SUN_DIST:         66.83 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      198.01d {+13h 12m 02s}  -10.95d {-10d 56' 54"}
MOON_DIST:       128.74 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       48.73,-45.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.07,  2.80 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:15:59 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1423875,   Seg_Num: 0
GRB_RA:          330.2114d {+22h 00m 50.73s} (J2000),
                 330.5554d {+22h 02m 13.28s} (current),
                 329.5480d {+21h 58m 11.53s} (1950)
GRB_DEC:          -9.1625d {-09d 09' 44.9"} (J2000),
                  -9.0369d {-09d 02' 12.8"} (current),
                  -9.4033d {-09d 24' 11.9"} (1950)
GRB_ERROR:       3.5 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  21023 TJD;   348 DOY;   25/12/14
IMG_START_TIME:  32642.00 SOD {09:04:02.00} UT,   104.5 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       261.98d {+17h 27m 54s}  -23.23d {-23d 13' 48"}
SUN_DIST:         66.83 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      198.01d {+13h 12m 03s}  -10.95d {-10d 57' 01"}
MOON_DIST:       128.74 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       48.74,-45.96 [deg] galactic lon,lat of the burst
ECL_COORDS:      329.07,  2.81 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See https://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 1.1% < P(seren) < 2.8%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:14:23 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1423875,   Seg_Num: 0
POINT_RA:        330.212d {+22h 00m 51s} (J2000)
POINT_DEC:        -9.170d {-09d 10' 10"} (J2000)
POINT_ROLL:      248.557d
IMG_START_DATE:  21023 TJD;   348 DOY;   25/12/14
IMG_START_TIME:  32601.51 SOD {09:03:21.51} UT,   64.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.085
N_STARS:         55
X_OFFSET:        440 [pixels]
Y_OFFSET:        586 [pixels]
X_MAX:           1399 [pixels]
Y_MAX:           1545 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw01423875000msufc0063.fits
SUN_POSTN:       261.97d {+17h 27m 54s}  -23.23d {-23d 13' 47"}
SUN_DIST:         66.83 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      198.00d {+13h 12m 00s}  -10.94d {-10d 56' 40"}
MOON_DIST:       128.75 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       48.73,-45.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.07,  2.80 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:26:15 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1423875,   Seg_Num: 0
POINT_RA:        330.211d {+22h 00m 51s} (J2000)
POINT_DEC:        -9.171d {-09d 10' 13"} (J2000)
POINT_ROLL:      248.556d
IMG_START_DATE:  21023 TJD;   348 DOY;   25/12/14
IMG_START_TIME:  33415.92 SOD {09:16:55.92} UT,   878.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.932
N_STARS:         118
X_OFFSET:        200 [pixels]
Y_OFFSET:        346 [pixels]
X_MAX:           1639 [pixels]
Y_MAX:           1785 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw01423875000msufc0878.fits
SUN_POSTN:       261.98d {+17h 27m 56s}  -23.23d {-23d 13' 49"}
SUN_DIST:         66.82 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      198.09d {+13h 12m 22s}  -10.99d {-10d 59' 17"}
MOON_DIST:       128.65 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       48.73,-45.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.07,  2.80 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:26:28 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1423875,   Seg_Num: 0
POINT_RA:        330.211d {+22h 00m 51s} (J2000)
POINT_DEC:        -9.171d {-09d 10' 13"} (J2000)
POINT_ROLL:      248.556d
IMG_START_DATE:  21023 TJD;   348 DOY;   25/12/14
IMG_START_TIME:  33415.92 SOD {09:16:55.92} UT,   878.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.932
N_STARS:         118
X_OFFSET:        200 [pixels]
Y_OFFSET:        346 [pixels]
X_MAX:           1639 [pixels]
Y_MAX:           1785 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw01423875000msufc0878.fits
SUN_POSTN:       261.98d {+17h 27m 56s}  -23.23d {-23d 13' 49"}
SUN_DIST:         66.82 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      198.09d {+13h 12m 22s}  -10.99d {-10d 59' 20"}
MOON_DIST:       128.65 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       48.73,-45.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.07,  2.80 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:26:39 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1423875,   Seg_Num: 0
GRB_RA:          330.2109d {+22h 00m 50.61s} (J2000),
                 330.5549d {+22h 02m 13.16s} (current),
                 329.5475d {+21h 58m 11.41s} (1950)
GRB_DEC:          -9.1633d {-09d 09' 47.8"} (J2000),
                  -9.0377d {-09d 02' 15.7"} (current),
                  -9.4041d {-09d 24' 14.8"} (1950)
GRB_ERROR:       1.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  21023 TJD;   348 DOY;   25/12/14
IMG_START_TIME:  32642.00 SOD {09:04:02.00} UT,   104.5 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       261.98d {+17h 27m 56s}  -23.23d {-23d 13' 49"}
SUN_DIST:         66.83 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      198.09d {+13h 12m 23s}  -10.99d {-10d 59' 22"}
MOON_DIST:       128.65 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       48.74,-45.96 [deg] galactic lon,lat of the burst
ECL_COORDS:      329.07,  2.81 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See https://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 1.1% < P(seren) < 2.8%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:27:44 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1423875,   Seg_Num: 0
POINT_RA:        330.211d {+22h 00m 51s} (J2000)
POINT_DEC:        -9.171d {-09d 10' 13"} (J2000)
ROLL:            248.556d
IMG_START_DATE:  21023 TJD;   348 DOY;   25/12/14
IMG_START_TIME:  33415.92 SOD {09:16:55.92} UT,   878.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     787396652
X_OFFSET:        759 [pixels]
Y_OFFSET:        905 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       919
Y_GRB_POS:       1065
BINNING_INDEX:   1
IM_URL:          sw01423875000msuni0915.fits
SUN_POSTN:       261.99d {+17h 27m 56s}  -23.23d {-23d 13' 49"}
SUN_DIST:         66.82 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      198.10d {+13h 12m 25s}  -10.99d {-10d 59' 36"}
MOON_DIST:       128.64 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       48.73,-45.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.07,  2.80 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:27:57 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1423875,   Seg_Num: 0
POINT_RA:        330.211d {+22h 00m 51s} (J2000)
POINT_DEC:        -9.171d {-09d 10' 13"} (J2000)
ROLL:            248.556d
IMG_START_DATE:  21023 TJD;   348 DOY;   25/12/14
IMG_START_TIME:  33415.92 SOD {09:16:55.92} UT,   878.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     787396652
X_OFFSET:        759 [pixels]
Y_OFFSET:        905 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       919
Y_GRB_POS:       1065
BINNING_INDEX:   1
IM_URL:          sw01423875000msuni0915.fits
SUN_POSTN:       261.99d {+17h 27m 56s}  -23.23d {-23d 13' 49"}
SUN_DIST:         66.82 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      198.10d {+13h 12m 25s}  -10.99d {-10d 59' 39"}
MOON_DIST:       128.63 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       48.73,-45.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.07,  2.80 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN Circular #43089
R. A. J. Eyles-Ferris (U Leicester), J. J. DeLaunay (PSU), R. Gupta (NASA GSFC), N. P. M. Kuin (UCL-MSSL), K. L. Page (U Leicester), D. M. Palmer (LANL) and T. M. Parsotan (GSFC) report on behalf of the Neil Gehrels Swift Observatory Team:
At 09:02:17 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 251214B (trigger=1423875). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 330.217, -9.167 which is
```
   RA(J2000) = 22h 00m 52s
   Dec(J2000) = -09d 10' 00"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a double-peaked structure with a duration of about 10 sec. The peak count rate was ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 09:03:18.2 UT, 60.7 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 330.21095, -9.16335 which is equivalent to:
```
   RA(J2000)  = 22h 00m 50.63s
   Dec(J2000) = -09d 09' 48.1"
```
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 25 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (4.01 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 5.2 (+2.80/-2.44) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 63 seconds after the BAT trigger. There is a candidate afterglow in the list of sources generated on-board at
```
  RA(J2000)  =	22:00:50.52 = 330.21052
  DEC(J2000) = -09:09:46.7  =  -9.16296
```
with a 90%-confidence error radius of about 1.10 arc sec. This position is 3.6 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.47. No correction has been made for the expected extinction corresponding to E(B-V) of 0.039.
Burst Advocate for this burst is R. A. J. Eyles-Ferris (raje1 AT leicester.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:20:02 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1423875,   Seg_Num: 0
POINT_RA:        330.211d {+22h 00m 51s} (J2000)
POINT_DEC:        -9.171d {-09d 10' 14"} (J2000)
ROLL:            248.557d
IMG_START_DATE:  21023 TJD;   348 DOY;   25/12/14
IMG_START_TIME:  32814.36 SOD {09:06:54.36} UT,   276.8 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     787396051
X_OFFSET:        759 [pixels]
Y_OFFSET:        905 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       919
Y_GRB_POS:       1065
BINNING_INDEX:   1
IM_URL:          sw01423875000msuni0313.fits
SUN_POSTN:       261.98d {+17h 27m 55s}  -23.23d {-23d 13' 48"}
SUN_DIST:         66.83 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      198.04d {+13h 12m 11s}  -10.97d {-10d 57' 55"}
MOON_DIST:       128.70 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       48.73,-45.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.07,  2.80 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:18:45 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     1423875,   Seg_Num: 0
GRB_RA:          330.2105d {+22h 00m 50.52s} (J2000),
                 330.5545d {+22h 02m 13.07s} (current),
                 329.5471d {+21h 58m 11.31s} (1950)
GRB_DEC:          -9.1629d {-09d 09' 46.4"} (J2000),
                  -9.0373d {-09d 02' 14.2"} (current),
                  -9.4037d {-09d 24' 13.3"} (1950)
GRB_ERROR:       1.1 [arcsec radius, statistical only]
GRB_MAG:         17.46 +/- 0.40 [mag]
FILTER:          10, White
IMG_START_DATE:  21023 TJD;   348 DOY;   25/12/14
IMG_START_TIME:  32598.00 SOD {09:03:18.00} UT,   60.5 [sec] since BAT Trigger Time
SUN_POSTN:       261.98d {+17h 27m 55s}  -23.23d {-23d 13' 48"}
SUN_DIST:         66.83 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      198.04d {+13h 12m 08s}  -10.96d {-10d 57' 38"}
MOON_DIST:       128.71 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       48.74,-45.96 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      329.07,  2.81 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        Result based on srclist data.  
COMMENTS:        Notice generated automatically.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 14 Dec 25 09:19:52 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1423875,   Seg_Num: 0
POINT_RA:        330.211d {+22h 00m 51s} (J2000)
POINT_DEC:        -9.171d {-09d 10' 14"} (J2000)
ROLL:            248.557d
IMG_START_DATE:  21023 TJD;   348 DOY;   25/12/14
IMG_START_TIME:  32814.36 SOD {09:06:54.36} UT,   276.8 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     787396051
X_OFFSET:        759 [pixels]
Y_OFFSET:        905 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       919
Y_GRB_POS:       1065
BINNING_INDEX:   1
IM_URL:          sw01423875000msuni0313.fits
SUN_POSTN:       261.98d {+17h 27m 55s}  -23.23d {-23d 13' 48"}
SUN_DIST:         66.83 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      198.04d {+13h 12m 10s}  -10.96d {-10d 57' 53"}
MOON_DIST:       128.70 [deg]
MOON_ILLUM:      26 [%]
GAL_COORDS:       48.73,-45.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.07,  2.80 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN Circular #43091
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the Swift GRB 251214B ( R. A. J. Eyles-Ferris et al., GCN 43089) errorbox 4148 sec after notice time and 4708 sec after trigger time at 2025-12-14 10:20:46 UT, with upper limit up to 17.4 mag. Observations started at twilight. The observations began at zenith distance = 61 deg. The sun altitude is -11.8 deg.
The galactic latitude b = -46 deg., longitude l = 50 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3070785
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

    4739 |        MASTER-Tunka |   C |    60 | 16.3 |        
    4799 |        MASTER-Tunka |   C |   180 | 17.4 |  Coadd 
    4739 |        MASTER-Tunka |   C |    60 | 15.9 |        
    4814 |        MASTER-Tunka |   C |    60 | 16.8 |        
    4814 |        MASTER-Tunka |   C |    60 | 16.4 |        
    4886 |        MASTER-Tunka |   C |    60 | 16.7 |        
    4886 |        MASTER-Tunka |   C |    60 | 17.0 |        
    4963 |        MASTER-Tunka |   C |    60 | 17.1 |        
    4963 |        MASTER-Tunka |   C |    60 | 16.8 |        
    5036 |        MASTER-Tunka |   C |    60 | 16.8 |        
    5036 |        MASTER-Tunka |   C |    60 | 16.5 |        
    5111 |        MASTER-Tunka |   C |    60 | 15.5 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
[1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html
GCN Circular #43093
Zhe Kang (CHO), Chao WU (NAOC), Liping Xin(NAOC), Xuhui Han(NAOC), Pinpin Zhang (NAOC), Xiaomeng Lu (NAOC), Zhenwei Li (CHO), You Lv (CHO), Ruosong Zhang (NAOC), Yujie Xiao(NAOC), Yulei Qiu(NAOC), Jing Wang (NAOC), Jinsong Deng(NAOC), Lei Huang(NAOC), Jianyan Wei (NAOC), report on behalf of the SVOM/C-GFT team:
We observed the field of GRB 251214B detected by Fermi/GBM (Fermi GBM team, GCN 43088) and Swift/BAT (Eyles-Ferris et al., GCN 43089) with LATIOS on SVOM/C-GFT. Observations started at 2025-12-14T09:12:24 UTC, ~10.12 min after the trigger.
The optical counterpart (Eyles-Ferris et al., GCN 43089) was clearly detected in our stacked images of band g, r , and i. The magnitudes are:
```
|[date-obs(mid-time)] | Mid_t-T0(min) | exposure time (s) | band | mag (AB) | mag_err|
|--------------------|--------------|-------------------|------|----------|--------|
|2025-12-14T09:12:42 | 10.75   | 3x10 | i | 16.56 |0.070|
|2025-12-14T09:26:55 | 24.64   | 5x30 | g | 18.56 |0.090|
|2025-12-14T09:40:03 | 37.77   | 6x30 | r | 18.33 |0.050|
```
The photometry was calibrated against UCAC4 catalogue and no correction for Galactic dust extinction was applied.
We thank the observation assistants Chun-Lei Guo and Yin-Huai Hao at Jilin observatory for their excellent support.
The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching.
GCN Circular #43095
O.A.Gress, N.M.Budnev (ISU), V.M.Lipunov, P.Balanutsa, I.Panchenko, A.Kuznetsov, E.Gorbovskoy, G.Antipov, N. Tiurina, Ya.Kechin,A.Chasovnikov, D.Vlasenko, V.Shumkov, I.Ionov, Yu.Tselik(Lomonosov MSU, SAI, Moscow), R.Mirgazov, A.Diachok, O.Ershova (Irkutsk State University), R. Podesta, C.Francile, F. Podesta, E. Gonzalez (OAFA, San JuanUni.,Argentina); D.Buckley (SAAO), A. Sosnovskij (CrAO RAS), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysic Observatory, Mexico) V.M.Pillet, R.Rebolo Lopez (The Instituto de Astrofisica de Canarias,Spain)
MASTER OT J220050.55-090945.8 detection
MASTER-Tunka robotic telescope of MASTER Global Robotic Net (Lipunov et al. [1-4], http://observ.pereplet.ru ), started Fermi (GCN 43088) and Swift (GCN 43089) GRB 251214B error-box observations after sunset at 2025-12-14 10:20:46 UT (Lipunov et al. GCN 43091, cover map https://master.sai.msu.ru/site/master2/event.php?id=3070779 )
MASTER auto-detection system found optical afterglow at summary images MASTER OT J220050.55-090945.8 , discovered by Swift (Eyles-Ferris et al. GCN 430089) and also observed by SVOM (Zhe Kang et al. GCN 43093) with unfiltered m_OT=19.5m at 2025-12-14 10:49:16UT.
There is SDSS galaxy (poss.host) in 0.067" in VIZIER database with z_phot=0.6634
Observation and reduction will continue.
```
[1] Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L
[2] Lipunov et al. 2022, Universe, Vol. 8(5), id.271
[3] Lipunov et a. 2019, ARep, vol.63, 293
[4] Lipunov V., Kornilov V., Gorbovskoy E., Tiurina N., Kuznetsov A. 2023,
Astronomical Robotic Networks and Operative Multichanel Astrophysics,Lomonosov MSU PRESS, 591pp.
http://www.pereplet.ru/lipunov/625.html#625
```
GCN Circular #43097
S.Y. Fu(HUST), D. Xu, Y.N. Zhu, P.L. Du, J.J. Jin, Z. Fan, X. Liu, L.B. He, J. An, S.Q. Jiang, Z.P. Zhu, J.J. Jia(NAOC)
We observed the field of GRB 251214B detected by Swift (Eyles-Ferris et al., GCN 43089) using the Xinglong-2.16m telescope equipped with the BFOSC camera. Observations started at 10:26:38 UT on 2025-12-14 (i.e., 1.41 h after the trigger), and a series of r- / g-band frames have been obtained.
The optical afterglow (Eyles-Ferris et al., GCN 43089; Kang et al., GCN 43093; Gress et al., GCN 43095) was clearly detected in our stacked frame with a magnitude of r = 19.40 +- 0.03 at a mid-time of 1.53 hr and g = 20.63 +- 0.09 at a mid-time of 1.88 hr, respectively, calibrated with Pan-STARRS1 DR2 catalog and not corrected for Galactic extinction.
We thank the staff at Xinglong observatory for their excellent support.
GCN Circular #43098
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 1446 s of XRT Photon Counting mode data and 1 UVOT images for GRB 251214B, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 330.21069, -9.16291 which is equivalent to:
```
RA (J2000): 22h 00m 50.57s
Dec (J2000): -09d 09' 46.5"
```
with an uncertainty of 2.1 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest position can be viewed at https://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #43100
Anshika Gupta, Dhruv Jain, Pankaj Pawar, Debalina Kar, and Kuntal Misra (ARIES) report:
We observed the field of GRB 251214B detected by Fermi/GBM (Fermi GBM team, GCN 43088) and Swift/BAT (Eyles-Ferris et al. 2025, GCN 43089) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-12-14 at 12:59:37 UT, i.e., ~ 3.95 hours after the Fermi/GBM trigger. We have taken multiple frames with an exposure time of 300s in the I filter. We stacked the images after the alignment. We detect an optical afterglow in our stacked image within the error box of Swift/UVOT (Eyles-Ferris et al. 2025, GCN 43089). We obtain the following preliminary magnitude in the stacked image:
```
Date Start_UT T_start-T0 (hour) Filter  Exp time (s)  Magnitude
===============================================================
2025-12-14  12:59:37    ~3.95   I     300s*18     20.03 +/-0.03
```
The optical detection of the burst is consistent with Eyles-Ferris et al. 2025 (GCN 43089); Lipunov et al. 2025 (GCN 43091); Kang et al. 2025 (GCN 43093); Gress et al. 2025 (GCN 43095); and Fu et al. 2025 (GCN 43097).
The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalogue.
GCN Circular #43103
Alan M. Watson (UNAM), Benjamin Schneider (LAM), Stéphane Basa (UAR Pytheas), Camila Angulo (UNAM), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Nikos Mandarakas (LAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), and Antonio de Ugarte Postigo (LAM) report:
We imaged the field of the Fermi/Swift GRB 251214B (Fermi GBM Team, GCN Circ. 43088; Eyles-Ferris et al., GCN Circ. 43089) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-12-15 01:33 to 03:22 UTC (from 16.52 to 18.34 hours after the Swift/BAT trigger) and obtained 28, 28, 28, and 84 minutes of simultaneous exposure in the g, r, i, and z filters, respectively.
The data were reduced, coadded, and analyzed with the ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
In our stacked images, at the position of the afterglow (Eyles-Ferris et al., GCN Circ. 43089; Kang et al., GCN Circ. 43093; Gress et al., GCN Circ. 43095; Fu et al., GCN Circ. 43097; and Gupta et al., GCN Circ 43100) we detect the a source with preliminary magnitudes of:
```
g = 22.97 +/- 0.21
r = 22.05 +/- 0.12
i = 21.52 +/- 0.12
z = 20.97 +/- 0.08
```
We note the presence of a bright galaxy coincident with the afterglow in Legacy Survey observations (Dey et al. 2019) with g = 23.70 +/- 0.11, r = 22.37 +/- 0.06, i = 21.62 +/- 0.06, z = 21.12 +/- 0.04, and a photometric redshift of z = 0.70 +/- 0.07. We suggest this might be the host galaxy. Its low redshift is consistent with the detection of the afterglow in g by Kang et al. (GCN Circ. 43093) and in our observations.
Our observations include light from both the afterglow and this galaxy, and the afterglow is only clearly detected above the galaxy in g. The fading in g between the observations of Kang et al. (GCN Circ. 43093) and our observations implies a temporal power-law index of 1.08 or steeper.
We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.
COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.
GCN Circular #43105
N.P.M. Kuin (MSSL/UCL) and R. Eyles-Ferris (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 251214B 64 s after the BAT trigger (Eyles-Ferris et al., GCN Circ. 43089). A source consistent with the XRT position Evans et al. GCN Circ. 43098) is detected in the initial UVOT exposures.
There were early reports of the optical afterglow from Zhe Kang et al. (GCN Circ. 43093) and S.Y. Fu et al. (GCN Circ. 43097).
The preliminary UVOT position is:
```
    RA  (J2000) =  22:00:50.53 = 330.21053 (deg.)
    Dec (J2000) = -09:09:46.4  =  -9.16290 (deg.)
```
with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white               64          214          147         17.21 +/- 0.03
v                  606          800           39         17.09 +/- 0.17
b                  532          724           39         18.08 +/- 0.17
u                  277          527          246         17.76 +/- 0.08
w1                 655         1472           97        >18.9
m2                 630         1447           97        >20.3
w2                 582         5213          136        >19.6
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.039 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #43112
D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), S. Campana (INAF-OAB), S. Lanava (PSU), S. Dichiara (PSU) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 5.9 ks of XRT data for GRB 251214B, from 46 s to 28.7 ks after the trigger. The data comprise 8 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode.
The light curve can be modelled with an initial power-law decay with an index of alpha=0.72 (+0.14, -0.17), followed by a break at T+418 s to an alpha of 1.33 (+0.10, -0.08).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.82 (+0.19, -0.18). The best-fitting absorption column is 1.6 (+0.7, -0.6) x 10^21 cm^-2, in excess of the Galactic value of 4.0 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.9 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.6 (+0.7, -0.6) x 10^21 cm^-2
Galactic foreground: 4.0 x 10^20 cm^-2
Excess significance: 3.5 sigma
Photon index:	     1.82 (+0.19, -0.18)
```
If the light curve continues to decay with a power-law decay index of 1.33, the count rate at T+24 hours will be 1.6 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.3 x 10^-14 (7.8 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01423875.
This circular is an official product of the Swift-XRT team.
GCN Circular #43113
Xing-Hao Luo, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:
GECAM-B was triggered in-flight by GRB 251214B, at 2025-12-14T09:02:19.10 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43088).
According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 17.7 +1.8/-1.2 s.
The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251214B.png
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).
GCN Circular #43120
M. Dafcikova (MUNI) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 09:02:18.03 UT on 14 December 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251214B (trigger 787395743/251214377), which was also detected by Swift BAT (R. A. J. Eyles-Ferris et al. 2025, GCN 43089) and GECAM-B (X. H. Luo et al. 2025, GCN 43113). The Fermi GBM on-ground location is consistent with the Swift BAT position.
The angle from the Fermi LAT boresight is 97 degrees.
The GBM light curve consists of a double-peaked emission with a duration (T90) of about 15 s (50-300 keV). The time-averaged spectrum from T0-0.6 to T0+9.9 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.81 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 1280 +/- 80 keV.
The event fluence (10-1000 keV) in this time interval is (1.3 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.58 s in the 10-1000 keV band is 3.3 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular #43123
I. Pérez-Fournon (IAC and ULL), F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia, E. Lekaroz-Urriza, M. Quintana-Ansaldo (all ULL), and A. López-Oramas (IAC and ULL)
Following the detection of the long GRB 251214B, detected by Fermi GBM (Fermi GBM team, GCN #43088), Swift BAT, XRT, and UVOT (Eyles-Ferris et al., GCN #43089; Evans et al., GCN #43098; Kuin and Eyles-Ferris, GCN #43105; and Burrows et al., GCN #43112), and GECAM-B (Luo et al., GCN #43113), we observed the field with one of the two Las Cumbres Observatory (LCO) 1-m telescopes equipped with Sinistro cameras located at the LCO node at Siding Spring Observatory near Coonabarabran, New South Wales, Australia. The observation, a single exposure of 60 sec in the SDSS r' filter, started on 2025-12-14 at 10:26:57 UT, about 1.41 hours after the Fermi, Swift, and GECAM-B triggers. The optical counterpart first detected by Swift UVOT (Eyles-Ferris et al., GCN #43089) is clearly detected in our image with a preliminary magnitude of r' = 19.18 +/- 0.10, calibrated against PanSTARRS-1 DR2 stars and not corrected for Galactic extinction. Our result is consistent with other optical and UV detections (Eyles-Ferris et al., GCN 43089; Kang et al., GCN #43093; Gress et al., GCN #43095; Fu et al., GCN #43097; Gupta et al., GCN #43100; Watson et al., GCN #43103; and Kuin and Eyles-Ferris, GCN #43105).
Our preliminary photometry is not corrected for the light of the likely host galaxy discussed by Gress et al. (GCN #43095), and Watson et al. (GCN #43103) at a photometric redshift of z = 0.709 +/- 0.078 (Duncan, 2022).
This work makes use of observations from the Las Cumbres Observatory global telescope network (LCO program IAC2025B-008, SGLF and Superluminous Supernovae surveys).
This work made use of the Astro-COLIBRI platform (P. Reichherzer et al. 2021, ApJS, 256, 5).
GCN Circular #43124
A. A. Volnova (IKI), R. Ya. Inasaridze (AbAO), A. S. Pozanenko (IKI), N. S. Pankov (HSE, IKI) report on behalf of IKI-GRB-FuN:
We observed the field of the long GRB 251214B detected by Fermi (Fermi team, GCN 43088), Swift (Eyles-Ferris et al., GCN 43089; Evans et al., GCN 43098; Kuin and Eyles-Ferris, GCN 43105; Burrows et al., GCN 43112), and GECAM-B (Luo et al., GCN 43113) with the AS-32 0.7m telescope of Abastumani Observatory (AbAO) taking several frames in R-band. The observations started on Dec. 14 at 15:00 UT, i.e., ~ 6 hours after the Swift/BAT trigger. In the stacked image we detect the optical afterglow reported previously (Eyles-Ferris et al., GCN 43089; Kang et al., GCN 43093; Gress et al., GCN 43095; Fu et al., GCN 43097; Gupta et al., GCN 43100; Watson et al., GCN 43103; Kuin and Eyles-Ferris, GCN 43105; Pérez-Fournon et al., GCN 43123). Preliminary photometry and observational details are the following:
```
Date        UT start  t-T0       Exp.    Filter   Obj.   Err.  UL         Site/Telescope
                     (mid,days)  (n*s)                         (3sigma)
2025-12-14  15:00:25  0.27325    51*60   R        20.6   0.2   20.7       AbAO/AS-32
```
The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction.
GCN Circular #43125
Y. H. Jiang (NJU), Y.-H. I. Yin (HKU), Y. Q. Zhao (PRIC,USTC), W. F. Wen (SZTU), H. Q. Cheng, and H. Sun (NAOC) on behalf of the Einstein Probe (EP) team:
We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP251214b. The transient triggered EP-WXT (ID: 01709250023) at 2025-12-14T07:20:22 (UTC), and followed by COLIBRÍ telescope and LCO (GCN 43090, GCN 43117). Ground analysis shows that the WXT position of the source is R.A. = 144.358 deg, DEC = -22.884 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). Due to the earth occultation, the WXT data only shows the decay of a flare starting from 2025-12-14T07:19:13.9 and lasts for around 120 s, with a peak flux of ~2 x 10^-9 erg/s/cm^2.
The average WXT 0.5 - 4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 4.02 x 10^20 cm^-2 and a photon index of 1.5 (-/+0.3). The derived average absorbed 0.5-4 keV flux is 1.1 (-/+0.2) x 10^-9 erg/s/cm^2.
We also note that EP251214b was only detected from ground analysis after restoring the data during the period of earth occultation, which leads to some delays in the analysis as well as the issuing.
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).
GCN Circular #43126
Y. H. Jiang (NJU), Y.-H. I. Yin (HKU), Y. Q. Zhao (PRIC,USTC), W. F. Wen (SZTU), H. Q. Cheng, and H. Sun (NAOC) on behalf of the Einstein Probe (EP) team:
We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP251214b. The transient triggered EP-WXT (ID: 01709250023) at 2025-12-14T07:20:22 (UTC), and followed by COLIBRÍ telescope and LCO (GCN 43090, GCN 43117). Ground analysis shows that the WXT position of the source is R.A. = 144.358 deg, DEC = -22.884 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). Due to the earth occultation, the WXT data only shows the decay of a flare starting from 2025-12-14T07:19:13.9 and lasts for around 120 s, with a peak flux of ~2 x 10^-9 erg/s/cm^2.
The average WXT 0.5 - 4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 4.02 x 10^20 cm^-2 and a photon index of 1.5 (-/+0.3). The derived average absorbed 0.5-4 keV flux is 1.1 (-/+0.2) x 10^-9 erg/s/cm^2.
We also note that EP251214b was only detected from ground analysis after restoring the data during the period of earth occultation, which leads to some delays in the analysis as well as the issuing.
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).
GCN Circular #43127
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP251214b ( EP Team et al., GCN 43125) errorbox 1777 sec after trigger time at 2025-12-14 07:49:59 UT, with upper limit up to 20.5 mag. The observations began at zenith distance = 14 deg. The sun altitude is -17.5 deg.
The galactic latitude b = 22 deg., longitude l = 256 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3071744
We obtain a following upper limits.
```
Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    1807 | 2025-12-14 07:49:59 |         MASTER-OAFA | (09h 37m 50.45s , -22d 35m 38.5s) |   C |    60 | 20.5 |        
    1873 | 2025-12-14 07:51:04 |         MASTER-OAFA | (09h 37m 50.56s , -22d 35m 35.8s) |   C |    60 | 20.5 |        
    1939 | 2025-12-14 07:52:10 |         MASTER-OAFA | (09h 37m 50.68s , -22d 35m 33.3s) |   C |    60 | 20.5 |        
    2004 | 2025-12-14 07:53:16 |         MASTER-OAFA | (09h 37m 50.79s , -22d 35m 30.8s) |   C |    60 | 20.4 |        
    2070 | 2025-12-14 07:54:22 |         MASTER-OAFA | (09h 37m 50.91s , -22d 35m 28.4s) |   C |    60 | 20.4 |        
    2137 | 2025-12-14 07:55:28 |         MASTER-OAFA | (09h 37m 51.00s , -22d 35m 26.1s) |   C |    60 | 20.5 |        
    2202 | 2025-12-14 07:56:34 |         MASTER-OAFA | (09h 37m 51.12s , -22d 35m 23.9s) |   C |    60 | 20.4 |        
    2268 | 2025-12-14 07:57:39 |         MASTER-OAFA | (09h 37m 51.21s , -22d 35m 21.8s) |   C |    60 | 20.5 |        
    2334 | 2025-12-14 07:58:45 |         MASTER-OAFA | (09h 37m 51.29s , -22d 35m 19.7s) |   C |    60 | 20.5 |        
    2399 | 2025-12-14 07:59:51 |         MASTER-OAFA | (09h 37m 51.36s , -22d 35m 17.2s) |   C |    60 | 20.4 |        
    2465 | 2025-12-14 08:00:57 |         MASTER-OAFA | (09h 37m 51.42s , -22d 35m 15.1s) |   C |    60 | 20.5 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
[1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html
GCN Circular #43129
S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC), R. A. J. Eyles-Ferris (U Leicester), R. Gupta (GSFC), H. A. Krimm (NSF), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 251214B (trigger #1423875) (Eyles-Ferris, et al., GCN Circ. 43089). The BAT ground-calculated position is RA, Dec = 330.222, -9.155 deg which is
```
   RA(J2000)  =  22h 00m 53.4s 
   Dec(J2000) = -09d 09' 17.3" 
```
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 99%.
The mask-weighted BAT light curve shows a double-peaked structure with a duration of about 10 sec T90 (15-350 keV) is 9.38 +- 0.73 sec (estimated error including systematics).
The time-averaged spectrum from T-0.19 to T+9.97 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.79 +- 0.12. The fluence in the 15-150 keV band is 5.0 +- 0.4 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-0.13 sec in the 15-150 keV band is 2.0 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1423875
GCN Circular #43131
A. de Ugarte Postigo (LAM), D. B. Malesani (DAWN/NBI and Radboud), M. Garnichey (LUX-Paris Obs.), J. An (NAOC), G. Corcoran (UCD), L. Izzo (INAF/OACn & DARK/NBI), A. Martin-Carrillo (UCD), A. Saccardi (CEA/Irfu), A. L. Thakur (INAF/IAPS), A. Torralba (ISTA) and Y. Ma (Princeton U.) report on behalf of the Stargate collaboration:
We observed the optical counterpart of GRB 251214B detected by Fermi (Fermi GBM team, GCN 43088), Swift (Eyles-Ferris et al., GCN 43089) and GECAM-B (Luo et al., GCN 43113) with X-shooter mounted on the UT3 (Melipal) of ESO’s Very Large Telescope (Paranal Observatory, Chile). Observations were conducted in twilight and at large airmass.
The acquisition images, which started at 00:46:54 UT of 15 Dec 2025 (15.74 hr after the burst onset) show the counterpart with the following photometry (AB magnitudes), as compared to field stars from the SDSS catalogue:
```
g = 23.15 +/- 0.06
r = 22.19 +/- 0.04
z = 20.76 +/- 0.05
```
A 2x600 s spectrum followed, covering the spectral range between 3000 and 21000 AA. The spectrum shows a red continuum, consistent with the photometry, only detectable above 6000 AA, and more prominent at infrared wavelengths. We do not detect clear emission features from the underlying host galaxy (mentioned by Gress et al., GCN 43095 and Watson et al., GCN 43103), which prevents us from measuring its redshift. We note that the Legacy Survey reveals that the source underlying the afterglow is composed of two blobs, a fainter one right under the GRB and a brighter one towards the North East, at a distance of 1". The slight difference between our photometry and the one of COLIBRÍ (Watson et al., GCN 43103) could be due to the different contribution of these underlying sources within the photometric aperture.
We acknowledge expert support from the ESO observing staff in Paranal, in particular Claudia Paladini, Célia Desgrange, Cecila Bustos, and Ana Jimenez-Gallardo.
GCN Circular #43132
N. S. Pankov (HSE, IKI), A. Kochergin (UAFO IAA), A. A. Volnova (IKI), A. S. Pozanenko (IKI) report on behalf of IKI-GRB-FuN:
We observed the field of the long GRB 251214B detected by Fermi (Fermi team, GCN 43088), Swift (Eyles-Ferris et al., GCN 43089; Evans et al., GCN 43098; Kuin and Eyles-Ferris, GCN 43105; Burrows et al., GCN 43112; Laha et al., GCN 43129), and GECAM-B (Luo et al., GCN 43113) with the RC-500 (0.5m) telescope of Ussuriysk Astrophysical Observatory (UAFO) taking several frames in R-band. The observations started on Dec. 14 at 10:44 UT, i.e., ~ 1.5 hours after the Swift/BAT trigger. In the stacked image we do not detect the optical counterpart reported previously (Eyles-Ferris et al., GCN 43089; Kang et al., GCN 43093; Gress et al., GCN 43095; Fu et al., GCN 43097; Gupta et al., GCN 43100; Watson et al., GCN 43103; Kuin and Eyles-Ferris, GCN 43105; Pérez-Fournon et al., GCN 43123; Volnova et al., GCN 43124; de Ugarte Postigo et al., GCN 43131). Photometry and observational details are the following:
```
Date        UT start  t-T0       Exp.    Filter   Obj.   Err.  UL         Site/Telescope
                     (mid,days)  (n*s)                         (3sigma)
2025-12-14  10:44:26  0.09073    57*60   R        n/d    n/d   19.4       UAFO/RC500
```
The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction.
GCN Circular #43134
Weikang Lin, Guowang Du, Ziwei Li, Brajesh Kumar, Jiayu Qi, Donglin Gao, Yu Pan, Yuan Fang, Xinlei Chen, Xingzhu Zou, Xufeng Zhu, Tao Wang, Jinghua Zhang, Xinzhong Er, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team:
We performed simultaneous multi-band photometric observations of GRB 251214B (Fermi GBM Team, GCN Circ. 43088; Eyles-Ferris et al., GCN Circ. 43089) with the newly installed three mosaic cameras on the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at the Lijiang Observatory. The observations were initiated at 11:31:54UTC2025-12-14 (~2.5 hours after the Swift/BAT trigger). Multiple frames were obtained in uvgriz - bands. The optical counterpart is detected in the stacked images of g, r bands and single frames of i, z bands, but there is no detection in the u and v band stacked images. The preliminary photometric magnitudes and 3-sigma upper limits are listed below. These magnitudes are not corrected for the Galactic extinction in the direction of the burst.
```
UT Start             |Band | Exposure(s)| mag/LimMag (AB) 
---------------------|-----|------------|----------------
2025-12-14T11:49:07  | u   |  300.0*2   |  >22.68
2025-12-14T11:31:54  | v   |  300.0*2   |  >22.47 
2025-12-14T11:49:09  | g   |  300.0*2   |  21.08 (+/-0.12)
2025-12-14T11:31:56  | r   |  300.0*2   |  20.64 (+/-0.08)
2025-12-14T11:49:09  | i   |  300.0     |  19.50 (+/-0.07)
2025-12-14T11:31:56  | z   |  300.0     |  18.60 (+/-0.14)
```
The optical detection of the burst is consistent with Eyles-Ferris et al. 2025 (GCN 43089); Kang et al. 2025 (GCN 43093); Gress et al. 2025 (GCN 43095); Fu et al. 2025 (GCN 43097); Gupta et al. 2025 (GCN 43100); Watson et al. (GCN 43103); Kuin et al. (GCN 43105); Pérez-Fournon (GCN 43123); Volnova et al. (GCN 43124); Postigo et al. (GCN 43131).
-------------------------------------------------------------------------------------------------
Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The Mephisto mosaic cameras were installed in October 2025. The first light was achieved in all three channels on 10 October 2025, and these are currently in the commissioning phase. Here, we note that the current data processing pipeline is still at a preliminary stage, with flux calibration precision in each band at the level of about 5% or even higher.
-------------------------------------------------------------------------------------------------
GCN Circular #43138
WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and
Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, observed the field of EP251214b (Jiang et al.,
GCN 43125) starting at 08:17, Dec 14 UT, about 0.95 hours after
the trigger. A set of 29x60s and again 40x60s clear (roughly R)
filter images were obtained. In our coadd images, we did not detect
any new source within the EP-WXT error circle (Jiang et al., GCN
43125) down to limiting mag of 20.8 and 21.5 mag (Vega) at a
mid-time of 1.23 and 3.12 hours after the trigger. Our result is
consistent with the upper limit reported by other groups
(Eyles-Ferris et al., GCN 43117; Lipunov et al., GCN 43127).
GCN Circular #43141
A. A. Volnova (IKI), E. Klunko (ISTP), A. S. Pozanenko (IKI), N. S. Pankov (HSE, IKI) report on behalf of IKI-GRB-FuN:
We observed the field of the long GRB 251214B detected by Fermi (Fermi team, GCN 43088), Swift (Eyles-Ferris et al., GCN 43089; Evans et al., GCN 43098; Kuin and Eyles-Ferris, GCN 43105; Burrows et al., GCN 43112; Laha et al., GCN 43129), and GECAM-B (Luo et al., GCN 43113) with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) taking several 120-second expositions in R-band starting on Dec.15 UT 11:36:28. In the stacked image we do not detect the optical counterpart reported previously (Eyles-Ferris et al., GCN 43089; Kang et al., GCN 43093; Gress et al., GCN 43095; Fu et al., GCN 43097; Gupta et al., GCN 43100; Watson et al., GCN 43103; Kuin and Eyles-Ferris, GCN 43105; Pérez-Fournon et al., GCN 43123; Volnova et al., GCN 43124; de Ugarte Postigo et al., GCN 43131; Pankov et al., GCN 43132; Lin et al., GCN 43134). Preliminary photometry and observational details are the following:
```
Date        UT start  t-T0       Exp.    Filter  Obj.  Err.  UL       Site/Telescope
                     (mid,days)  (n*s)                      (3sigma)
2025-12-15  11:36:28  1.12792    30*120  R       n/d   n/d   22.6     Mondy/AZT-33IK
```
The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction.
GCN Circular #43149
P. Gokuldass (ERAU), F. George (UVI), N. Orange (OrangeWave Innovative Science, LLC), B. Gendre (UVI), D. Morris (NASA), and T. Lombardi (Eckerd College) report:
We observed the field of long GRB 251214B detected by Fermi (Fermi team, GCN 43088), Swift (Eyles-Ferris et al., GCN 43089; Kuin and Eyles-Ferris, GCN 43105; Burrows et al., GCN 43112), and GECAM-B (Luo et al., GCN 43113) with the 0.5m Virgin Island Robotic Telescope (VIRT) at the University of the Virgin Islands' Etelman Observatory on 2025-12-14 starting at 23:12:24.856 UTC (T-mid ~ T0 + ~15h). We performed a series of exposures in an R filter with a total exposure of 1210s. The weather conditions were partly cloudy during the hours of observation with an average airmass of 2.06.
We do not detect any source at the enhanced XRT position reported (Evans et al., GCN 43098). This non-detection is consistent with reported detections (Eyles-Ferris et al., GCN 43089; Kang et al., GCN 43093; Gress et al., GCN 43095; Fu et al., GCN 43097; Gupta et al., GCN 43100; Watson et al., GCN 43103; Kuin and Eyles-Ferris, GCN 43105; Pérez-Fournon et al., GCN 43123, de Ugarte Postigo et al., GCN 43131) and upper limits (Volnova et al., GCN 43124; Pankov et al., GCN 43132; Volnova et al., GCN 43141; Lin et al., GCN 43134).
We report the following 3-sigma upper limit:
```
T_mid                ||Exposure   ||Filter   ||Limit 
T+ ~15h              ||  1210s    || R       || > 20.4
```
The limit is estimated from comparison to nearby Gaia D3 synphot stars and is not corrected for Galactic extinction. We acknowledge the use of STDWeb interface to verify our result.
We acknowledge financial support in part from NASA EPSCoR 80NNSC22M0063, NSF AST 2319415, and NASA EPSCoR 80NSSC24M0112. This message can be cited.

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Jochen Greiner, last update: 18-Dec-2025 [Disclaimer]